Saw tooth

ABSTRACT

A saw tooth intended primarily for sawing wood, particularly in one direction of movement, and having a tip which is given an increased thickness in relation to the remainder of the tooth by upsetting or some other method, and bevelled surfaces so arranged that they form one or more oblique cutting edges presenting a clearance angle. The cutting edge or each of the cutting edges is formed by the intersecting line between a bevelled surface on an upper surface on the tooth and an under surface on said tooth. The bevel angle is at least 27* and at most 60*.

llite tts lrlsson [54] SAW TOUTH [22] Filed: Sept. 9, 11968 [21]Appl.No.: 758,488

3,372,719 3/1968 Shone ..l43/l41 FOREIGN PATENTS OR APPLICATIONS 764,36312/1956 Great Britain .l43/l 33 Primary Examiner-D0nald R. SchranAttorney-Young & Thompson [5 7] ABSTRACT A saw tooth intended primarilyfor sawing wood, particularly in one direction of movement, and having atip which is given an increased thickness in relation to the remainderof the tooth by upsetting or some other method, and bevelled surfaces soarranged that they form one or more oblique cutting edges presenting aclearance angle. The cutting edge or each of the cutting edges is formedby the intersecting line between a bevelled surface on an upper surfaceon the tooth and an under surface on said tooth. The bevel angle is atleast 27 and at most 60.

2 Claims, 28 Drawing Figures PATENTEDMAR28 I972 3,651,841

' sum 3 OF 3 INVENTOR.

01 T'JW SAW TOOTH The present invention is concerned with a saw toothprimarily for cutting wood, particularly in one direction of movementprovided with a tip which has been given increased thickness in relationto the remainder of the tooth by upsetting, swaging or some othermethod. In general, saw teeth of this type have been found to givebetter results than the older type of teeth which have been set. At thebeginning, saw teeth provided with tips of the type described had acutting edge which was directed transversely and perpendicular to theplanar side surfaces of the saw blade, and a length which was somewhatlonger than the thickness of said blade. It is now also known to providesuch teeth with bevelled surfaces, arranged so that they form at leastone oblique cutting edge presenting a clearance angle.

These saw teeth were admittedly an improvement on the set teeth, butboth the perpendicular cutting edge and the oblique edge presenting aclearance angle function essentially like a chisel and produce short,particulate chips and a relatively rough cut.

The invention, which can be applied to sawing devices of the most widelydiffering types, including sash saws, circular saws and hand saws, isintended to eliminate these disadvantages, and a saw tooth designedaccording to the invention is, for this purpose, mainly characterized inthat the cutting edge or each of the cutting edges is formed by theintersecting line between a bevelled surface on the upper surface of thetooth and an under surface on said tooth, and that the bevel angle is atleast 27 and at most 60. The advantage presented by the oblique cuttingedges according to the invention over the known transversely directedcutting edges is that they cut cleanly, like a knife, which means that asaw tooth designed in accordance with the invention gives a longer, andin the case of cellulose digesting processes, fiberboard manufacturingprocesses etc., a more useful chip besides leaving a smoother cutsurface on the sawn wood. In addition to the two aforementionedadvantages, saws provided with teeth designed according to the inventionhave also been found to possess a greater cutting ability than teethused hitherto, which has enabled the feed to be increased by 50 percentwith unchanged overhang; i.e., the angle at which the blade meets thewood. Furthermore, the risk of misfunction clue to heat is less,operation quieter and the power consumption lower. One factorcontributing to the good result obtained with respect to reciprocatingsaw blades is that the teeth according to the invention scratch a grooveduring the idling stroke, which facilitates the sawing operation on theworking stroke.

The invention will now be described with reference to the accompanyingdrawings, which show by way of example and in enlarged scale a portionof a sash saw provided with teeth designed according to the invention.In the drawings FIG. 1 is a fragmentary cross-sectional view of a sawtooth according to the present invention, taken on the line l1 of FIG.2;

FIG. 2 is a side elevational view of two saw teeth according to theembodiment ofFIG. 1;

FIG. 3 is a top plan view of FIG. 2;

FIGS. 4, 5 and 6 are views similar to FIGS. 1, 2 and 3, respectively,but showing a second embodiment of the invention;

FIGS. 7, 8 and 9 are views similar to FIGS. 1, 2 and 3, respectively,but showing a third embodiment of the invention;

FIGS. 10, 11 and 12 are views similar to FIGS. 1, 2 and 3, respectively,but showing a fourth embodiment of the invention;

FIGS. 13, 14 and 15 are views similar to FIGS. 1, 2 and 3, respectively,but showing a fifth embodiment of the invention;

FIG. 16 is an enlarged fragmentary view of a portion of FIG. 13;

FIGS. 17, 18 and 19 are views similar to FIGS. 1, 2 and 3, respectively,but showing a sixth embodiment of the invention;

FIGS. 20, 21 and 22 are views similar to FIGS. 1, 2 and 3, respectively,but showing a seventh embodiment of the invention;

FIGS. 23 and 24 are views similar to FIGS. 1 and 2, respectively, butshowing an eighth embodiment of the invention;

FIGS. 25 and 26 are views similar to FIGS. 1 and 2, respectively, butshowing a ninth embodiment of the invention; and

FIGS. 27 and 28 are views similar to FIGS. I and 2, respectively, butshowing a tenth embodiment of the invention.

FIGS. 1-3 show two saw teeth in an end view, a sideview and a view ofthe saw blade portion seen towards the tooth line. In this embodimentthe teeth according to the invention are bevelled alternately,everyother tooth 2a on the one and every other 2b on the other sidesurface,

FIGS. 4-6 illustrate embodiments of teeth which have an essentiallyparallel trapezium-shaped top surface,

FIGS. 7-9 and 10-12 show in corresponding views the oblique cuttingedges combined in one and the same tooth, which has a split form,

FIGS. 13-22 show the oblique cutting edges combined in the same tooth,which has been bevelled symmetrically on both side faces of the toothtip, and

FIGS. 23-28 illustrate how the various designs of the tooth tip can beproduced with hard metal cutting bits soldered to the tooth, the bitsbeing ground to present one or more oblique cutting edges according tothe invention.

In FIGS. 1-3 the reference numeral 1 identifies the saw blade proper,numerals 2a and 2b saw teeth with cutters alternating on either side ofthe saw blade, and numeral 3 the gap between the teeth. The teeth workin the direction of arrow 4. Each tooth has an under surface 5perpendicular to the sides of the blade and presenting a positivecutting angle a, and an upper surface 6 which slopes towards therearwardly lying tooth gap and presents a clearance angle 8. The uppersurface 6 is bevelled at the tip of the tooth, the plane of the bevel 7forming the angle y to the side surfaces of the blade. The intersectingline between the bevel surface 7 and the under surface 5 forms theoblique cutting edge 8 characteristic of the invention. The tips of theteeth have been made thicker than the actual saw blade, by upsetting, sothat the blade is able to pass freely in the cut during sawing.Projections or prominotories caused by the upsetting process areidentified by the reference numeral 9.

Full scale tests have shown that the positive cutting angle a cansubstantially be varied within the limits 5 and 30, the clearance angleB between 5 angle and the bevel angle y between 27 and 60. Excellentresults have been obtained during tests with single-bevel teeth shown inFIGS. 1-3, when y 35-45.

In the embodiment shown in FIGS. 1-3 the bevel surface 7 is essentiallytriangular in shape. This surface, which can also be designated topsurface, can however, according to the invention also essentially be inthe shape of a trapezoid, whereupon the saw teeth obtain the appearancedepicted in FIGS. 4-6. The reference numerals employed in the firstthree figures are also used to identify corresponding details infollowing figures. The bevelling in the embodiment shown in FIGS. 4-6produces good results if the bevel angle 7' is kept within the range of27-60 with a positive cutting angle a varying within the limits 5 and 30and the clearance angle 3 is between 5 and 35".

As previously mentioned, the oblique cutting edge according to theinvention can also be produced in ways other than shown in FIGS. 1-6.Thus it is possible to combine the alternating bevelling on both sidesurfaces of the teeth in one and the same tooth, whereupon the tip ofthe tooth obtains the V- shape depicted in FIGS. 7-9. In this way thetip of the tooth, which has been thickened by upsetting, for instance,obtains two small points 10 which present two opposing, oblique cuttingedges 11. The width of the saw tooth across the two points is equalizedto optimum measurements for free passage of the saw blade. The bevelangle 7 see FIG. 7, should be chosen between 27 and 60.

A saw tooth presenting principally the same form as that shown in FIGS.7-9 can be obtained by upsetting and grinding. As will be seen fromFIGS. 10-12, this embodiment lacks the projections or prominotories 9,which are formed in the embodiments previously described.

According to a modification of the invention, two oblique cutting edgescan also be obtained by double-side bevelling on the outside of an upsettooth, as shown in FIGS. 13-16. In this instance a symmetric tip 12 isobtained on each tooth with the two oblique cutting edges 13. The bevelangle 7 (see the enlarged view in FIG. 16) which in this instance formshalf the rake angle of the tip should lie within the range of to 60. Thegreatest thickness A of the tip, produced by upsetting, for instance, isequalized to a smaller measurement B, which affords clearance in thecutter. The measurement C is the thickness of the saw blade 1.

A saw tooth principally of the same design as shown in FIGS 13-16 can beobtained by an upsetting process, which may not require a subsequentgrinding process. An illustration of a saw tooth produced in this manneris given in FIGS. 17-22, of which FIGS. 17-19 and 20-22 show in directlycomparable views the appearance of two teeth of this type presentingdifferent rake angles. The tooth shown in FIGS. 17-19 has a rake angleof 90, i.e., a bevel angle 7 of 45, whereas the tooth shown in FIGS.20-22 has a rake angle of half the size, that is 45, and hence has abevel angle 7 of only 22.5".

If the tip of the saw tooth is given increased thickness by fixing hardmetal bits thereto, the bits can be bevelled in accordance with theinvention by grinding, so that the tip obtains an oblique cutting edgeor cutting edges with clearance. This is illustrated in the pairs ofFIGS. 23-24 up to and including 27-28, which show how hard metal bits16, 17, 18 fixed to the tip of the tooth have been bevelled and haveobtained cutting edges according to the previously described embodimentsof the invention.

The saw tooth according to the invention has been particularly tested insash saws, but in addition to being used for sawing wood and otherorganic material such as bone, cork, rubber and plastic material mayalso be used, subsequent to making suitable adjustment to the cuttingangle and cutting speeds, for sawing metals.

What I claim is:

1. A saw tooth having a tip which has a greater thickness than the restof the tooth, said saw tooth having thereon bevelled surfaces formingthe tip of the tooth and so disposed that they form a straight obliquecutting edge, said tooth having a substantial clearance angle of 5 to 45on its rear outer side, said cutting edge being the intersection betweena bevelled surface on the outer side of the tooth and a forward undersurface of the tooth disposed at a positive cutting angle of 5 to 30,said bevelled surface being disposed at an angle of 27 to 60 to theplane in which the tooth moves.

2. A saw tooth as claimed in claim 1, in which said bevelled surface isdisposed at an angle of 35 to 45 to the plane in which the tooth moves.

1. A saw tooth having a tip which has a greater thickness than the restof the tooth, said saw tooth having thereon bevelled surfaces formingthe tip of the tooth and so disposed that they form a straight obliquecutting edge, said tooth having a substantial clearance angle of 5* to45* on its rear outer side, said cutting edge being the intersectionbetween a bevelled surface on the outer side of the tooth and a forwardunder surface of the tooth disposed at a positive cutting angle of 5* to30*, said bevelled surface being disposed at an angle of 27* to 60* tothe plane in which the tooth moves.
 2. A saw tooth as claimed in claim1, in which said bevelled surface is disposed at an angle of 35* to 45*to the plane in which the tooth moves.